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Патент USA US2069471

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Feb. 2, 1937.
‘
D. J. BAKER
ANTIFRICT ION SCREW
‘Filed June 19, 1936
2,069,471
2 Sheets-Sheet 1
\DOWJBMG’IT.
2,069,471
Patented Feb. 2, 1931
UNITED STATES PATENT OFFICE
2,069,471
ANTIFRICTION SCREW
Donald J. Baker, Pasadena, Calif.
Application sum 19, 1936, Serial No. 86,188
10 Claims.
This invention relates to a screw and nut
assembly and in particular to constructions em
ploying ball and/or roller bearings for reducing
5
1 UK
the friction between a screw and a cooperating
nut.
A general object of the invention is to devise
an improved construction of ball-bearing or
roller-bearing screws for carrying greater loads.
A speci?c object of the invention is to devise an
improved retainer o-r cage for the anti-friction
bearings which takes up very little space between
the screw and the nut. A further object is to
devise an improved thread construction in the
nut and screw assembly which will permit the
ball or roller races on both the screw and the
nut to be formed by grinding operations.
The constructions of my invention are capable
of general use in “any situation where screws
are useful, such as in lifting jacks, pumps, presses
and the like.
My invention is illustrated in the drawings in
which:
(Cl. 74-459)
vided with a. helical thread 4 of the same pitch
as the screw thread 2, and this thread is pref
erably formed with a lower side 4a. arranged at
45 degrees to the axis of the thread or parallel
with the upper face 20. of the screw thread 2, and
a ball race 4b is formed along the upper edge
of the thread 4. The ball race 4b is also prefer
ably formed as the arc of a quarter-circle and is
transversely inclined to the axis of the nut by
an angle of 45 degrees.
10
The screw l is supported within the nut 3 by ‘
means of a series of balls 5 which are arranged
about the screw and are seated in the ball-race
4b formed on the thread of the nut and engage
the ball-race 2b formed on the thread of the 15
screw. The balls 5 are maintained in proper
spaced relation by a retainer or cage 6 which
is preferably formed as a shell-like member hav
ing a threaded exterior and a threaded interior
of the same pitch as the nut and screw threads 20
and having a shape closely conforming with‘the
threads on the nut and the screw. As will be
seen from Figure l, the upper end of the retainer
comprising the three upper convolutions of the
thread is shown in elevation, while the lower por 25
tion is shown in section. The retainer is prefer
Figure l is a view showing one arrangement of
ball-bearing screw and nut assembly in side ele
vation with parts of the assembly shown in sec
25
tion;
' ably formed of two helical walls 6a and 6b ar
Figure 2 is an enlarged fragmentary sectional ranged at right angles to each‘ other and each
view taken along line 2-—2 of Figure 1;
'_ being transversely) inclined at an angle of 45 de
Figure 3 is an. enlarged detailed view showing grees to the axis of the screw. The wall 6b is
30
the manner of mounting a ball in the ball re-x of su?icient thickness to serve as a carrier for
30
tainer;
the balls 5, while the walls 6a may be reduced in ,
Figure 4 is a fragmentary View, partly in sec
section to a thickness su?icient only to give the
tion and partly in elevation, showing another required strength or rigidity to the retainer.
arrangement of ball bearing screw and'nut as ' The retainer 6 may be formed by die-casting, or
sembly in which ball races are provided on both it may be formed from solid or tubular stock by
35
sides of the screw thread;v
'
machining the thread-like outer and inner sur
Figure 5 is a fragmentary enlarged sectional faces on a lathe, or, if desired, the retainer may
view showing a modi?ed method of mounting the be formed by two separate helical strips, one
balls in the retainer;
_
forming the wall 6a. and the other forming the 40
Figure 6 is a fragmentary view, partly in sec
wall 61), and the two being suitably joined to
40 tion and partly in elevation, illustrating a nut
gether as by welding along the edges. If desired,
and screw assembly employing roller bearings; the retainer may be formed of a single helical
strip formed in the shape of wall 6b, and. for the
and
Figure 7 is a fragmentary vertical sectional purpose of re-enforclng the retainer, jumper 45
view showing a modi?ed arrangement of roller strips may be secured across adjacent edges of
45 bearings on each side of the threads of the
adjacent convolutions of the strip.
nut and screw.
.
'
One method of mounting the balls in the re
Referring to Figure 1 the screw I is provided _ tainer 6 is illustrated in Figure ;3. First, the holes
with a helical thread 2 formed thereon, the upper for? receiving the balls are formed by drilling
side 2a of the thread being preferably formed at - through the thick wall 6b from the outside of
50 an angle of 45 degrees to the axis of the shaft,
the retainer, and the drilling operation is stopped
and the lower face of the thread having a ball before the drill passes entirely through the wall
race 2b formed thereon, the race being prefer
so as to leave a tapered shoulder Be at the bottom .
ably formed as one quarter of the arc of the cir
of the hole. The drill is large enough to afford
cle and being transversely inclined at an angle
55 of 45 degrees to the axis of the screw. The axial adequate clearance f or the ball 5, and the shoulder
60 prevents the ball from passing through the
contour of the thread on the screw is shown hole. After the balls are placed in the holes of
at the bottom of the screw in the cross-hatched the. retainer, a retaining shoulder 6d similar to
area marker Ila. The nut which cooperates with shoulder to is formed around the edge of the hole 60
the screw is indicated at 3 in section and-is pro»
2
2,069,471
at the other face of the wall 6b in any desired
manner, as by a suitable swaging tool. The in
dentation formed by the swaging tool is shown at
Se in Figure 3. Any other suitable method of
retaining the balls in the holes may be employed.
The enlarged sectional view shown in Figure 2
illustrates the arrangement of the balls in the.
tures in any suitable manner as by pins 9 sup
ported in the wall 67) and freely passing through
the rollers 8.
The rollers 8 may be cylindrical in
shape, but in order to obtain better rolling action
I prefer to form them in a frusto-conical shape,
with the apex of the generating cone located sub
stantially on the axis of the screw.
retainer along the axis of the thread. The balls '
In order to provide a lateral bearing surface and
may be spaced apart any desired distance con
prevent lateral shifting of the screw, a shoulder
sistent with the load to be carried. It will be 20 may be formed on the inneryedge of the race
understood that the closer the spacing the greater 2b and a similar shoulder 4c may be formed on 10
the allowable load which can be carried by the the inner edge of the race 4b and these two shoul
screw, and the only limit to the closeness of ders cooperate with the opposing ends of the roll
spacing is the reduction of the material of the ,ers 8 to prevent excessive lateral play between
15 retainer between the balls to a point to weaken
the screw and the nut.
15
the retainer.
In Figure 7 I have illustrated a fourth modi
As will be understood by those skilled in the ?cation of a nut and screw assembly, and this
art, the nut may be held stationary and the screw arrangement corresponds to the arrangement
rotated, or vice versa. In any case, the retainer shown in Figure 4 except that roller bearings are
20 8 is free to rotate, and will rotate at half the
speed of the rotary element and will advance at
half theaxial speed as the movable element. Ac
cordingly, in designing a screw according to my
invention, in order that the race on the nut thread
25 shall be completely ?lled with balls or rollers at
all times, the retainer should have a length equal
to one-half of the distance of travel of the mov
able element plus the length of the nut.
In Figure 4, I have shown a modi?ed construc
30 tion similar to that illustrated in Figure 1, and
corresponding elements in these two ?gures are
indicated by the same reference numerals. In
this arrangement ball race 2a’ is formed on the
upper surface of the screw thread 2 while the op
posing ball race 4a’ is formed on the lower face
of the nut thread 4, and a series of balls 5' are
arranged between these two races. This con
struction also includes the ball races 2b and 4b,
with balls 5, the same as in Figure 1. With this
arrangement, the nut and screw assembly will
withstand a thrust-in either direction along its
axis, whereas in the arrangement of Figure 1,
axial thrust can be applied in one direction only.
The construction of the retainer 6 in Figure 4 is
45 substantially like that shown in Figure 1 in that
it is formed mainly of two helical walls arranged
at right angles to each other, but ball bearings
are supported in each helical wall instead 01' in
only one wall.
-
In Figure 5 I have illustrated amodi?ed ar
rangement for mounting the ball hearings in the
' retainer.
In this arrangement I have shown the
ball 5 as being mounted in a separate metallic
insert ‘I which in turn is supported in any suitable
55 manner in holes formed in the retainer wall 6b.
By employing a separate metallic retainer for
each individual ball, it is possible to first] mount
the ball within the retainer 1 separate from the
cage retainer 6, and then mount the unit assem
bly, including the ball 5 and the retainer 1, within
employed instead of ball bearings. As will be 20
seen from the drawings, the bearing retainer ele
ment also consists mainly of two helical walls hav
ing transverse inclinations of substantially 45 de
grees to the axis of the screw and being arranged
at right angles to each other. A series of rollers 25
8 are located between two opposing faces of the
threads of the nut and screw while a series of
rollers 8' are arranged between the two remain
ing opposing faces of the threads on the nut and
screw. As shown in Figure 7, I prefer to stagger 30
the rollers 8 and 8' in vertical spacing for con
venience in mounting the rollers within the re
tainer 6. Here also, the rollers are formed with
the frusto-conical shape with the apex of the
generating cone located substantially on the axis 35
of the screw.
From what has been said above, it will be clear
that due to the particular construction and ar
rangement of the retainer, the retainer takes up
very little space between the screw and the nut, 40
and it is, therefore, possible to employ a screw
having threads with an outside diameter equal to
or greater than the inside diameter of the thread
in the nut. This construction offers a greater
seating area for the balls and/or rollers and, 45
therefore, a correspondingly greater load carrying
capacity of the screw. Also, the particular shape
‘and arrangement of the two ball or roller races
provides lateral support for the screw and pre
vents wobbling of the screw.
Furthermore, by 50
forming the two races at an angle in the manner
described, it is possible to grind these races to
accurate shape, and this would not be possible in
case the races were formed in the side of a thread
of square cross-section. It will be understood that 55
the races may be ground to shape by means of a
grinding wheel of a smaller diameter than the in
side diameter of the thread on the nut and oper
ated on a spindle extending into the nut substan
tially parallel with the axis of the nut.
60
the cage retainer 6.
_ It will be noted that in all forms of my inven
In Figure 6 I have illustrated a nut and screw tion disclosed herein, the thread face extends be
assembly similar to that shown in Figure 1 but in low
the lower edge of the bearing race on the
which roller bearings are substituted for ball bear
root side of the thread, that is, the bearing race
ings. In this arrangement the races 2b and 4b - is spaced from the root of the thread. This con
are formed with straight transverse sections ar
struction permits the ball retainer to be formed 65
ranged at an angle of substantially 60 degrees to of
helical walls of straight transverse sections ar
the axis of the screw, and the two thread faces ranged at substantially right angles to each other,
2a and la have substantially straight transverse and it provides sui?cient room for the helical walls
70 sections arranged substantially at right angles to of the retainer to extend beyond the ball races
the faces 2b and 4b. The retainer 6 is also formed and to give adequate support for the balls as shown 70
of two helical walls 6a and 6b arranged at right in the various ?gures of the drawings.
angles to each other transversely. A series of
In the appended claims the terms “rolling hear
rollers l are mounted in apertures formed in hell
ing elements” and “anti-friction elements” are to
TI cal wall ‘D and may be retained in these aper
be interpreted broadly to apply to either a ball ele
75
3
. 2,069,471
bearing race formed on one face of said thread,
said race being arranged so that its lower edge is
ment or a roller element; the term “bearing race”
is to be broadly interpreted to apply to a race for
spaced from the root of said thre d.
.
5. In combination, a screw an a cooperating
either a ball or a roller; the term “complemental”
is used to de?ne the relation between the ex
terior and interior thead on the retainer whereby
nut, each provided with V-shaped threads, and
a plurality of roller bearing elements arranged
opposing faces of the threads ‘on said
transverse angular relations corresponding to the ' between
nut and having their axes directed substantially
angular relations of the faces of the thread.
While I prefer to use a 45 degree relation of the towards the axis ofsaid screw, said opposing 10
two
helical walls forming the cylindrical bearing ' thread faces being provided each with a shoulder
10
retainer in Figures 1, 4, and 7, which results in the cooperating with opposing ends of said rollers to
two walls being at right angles to each other, it prevent lateral displacement of said screw with
respect to the nut.
will be understood that this relation is not abso
the retainer is formed as two helical walls having
6. A retainer for rolling bearing elements com
prising a tubular member formed of a helical 15
wall of uniform thickness and having a trans
verse inclination of substantially 45 degrees to the
axis of the cylinder and a second helical wall of
lute but may be varied somewhat above or below
15 this angle. Also, the axis of the rollers 8 in Fig
ure 6 may vary from the 60 degree angular posi
tion with respect to the axis of the screw.
What I claim is: '
,_
uniform thickness joining adjacent edges of the
1. In combination, a screw and a cooperating
?rst helical wall and having a. transverse inclina 20
tion of substantially 90 degrees to the first helical
wall, one of said helical walls being thicker than
the other and being provided with a plurality of
spaced holes for receiving and retaining a plu
nut, each provided with V-shaped threads, a
bearing race formed on one face of the thread
of said screw and spaced from the root thereof, a
bearing race formed on an opposing face of the
thread of said nut and spaced from the root of
'7. A ball retainer comprising a tubular‘member
having a V-shaped threaded exterior and a
threaded interior complemental to the exterior,
the walls of said thread being arranged substan
tially at right angles to each other and a plu 30
rality of‘ balls supported in a plurality of holes
formed in one side-wall of said thread, each of
bearing elements in spaced relation, said retainer
comprising a tubular member formed of two heli
30 cal walls arranged substantially at right angles
to each other transversely thereof, one helical
wall being arranged between one pair of opposing
said balls being mounted in an individual retainer
ring which in turn is supported in a hole formed
faces of the threads on the nut and screw and the
other helical wall being arranged between the
other pair of opposing faces of the threads on the
nut and screw, said rolling bearing elements be
ing retained in holes formed in one of said helical
in said hollow cylinder.
_
walls.
ranged substantially at right angles to each other
35
8. A retainer for rolling bearing elements com
prising a tubular member formed of two helical
walls joined along their edges and being ar
>
2. In combination, a screw and a cooperating
~10
25
rality of rolling bearing elements.
25 the thread, a plurality of rolling bearing elements
arranged in said races, and a retainer located be
tween said screw and mat for maintaining said
transversely of their length, one of said helical 40
walls being provided with a plurality of holes
spaced along the length thereof, a rolling bear~
ing element arranged in each hole, and means
for retaining said elements in said holes inde
46
pendently of said screw and nut.
9. In“ combination, a screw and a cooperating
nut, each provided with V-shaped threads, the
faces of each of said threads being arranged sub
stantially at 90 degrees to each other, a bearing
race formed on one face of the thread of said
screw and spaced from the root thereof, a hear
ing race formed on an opposing face of the thread
of said nut and spaced from the root of the
thread, a plurality of rolling bearing elements
nut, each provided with V-shaped threads, the
walls of said threads being arranged substantially
arranged in said races, and a retainer located be
tween said screw and nut for maintaining said at right angles to each other, a plurality of roll
bearing elements in spaced relation, said retainer > ing bearing elements arranged between opposing 50
comprising a tubular member having a V-shaped faces of the threads of said nut and screw, a re
tainer located between said screw and said nut
thread formed on the exteriorthereof and a simi
for maintaining said bearing elements in spaced
lar thread formed on the interior in complemen
tal relation with the exterior thread, whereby said relation, said bearing elements comprising rollers
retainer is formed of two helical walls joined along mounted in individual holes formed in said re. 55
their edges, one helical wall being located between tainer, and means for mounting said rollers in one pair of opposing faces of the threads on the said holes with their axes directed towards the
screw and‘ nut while the other helical wall is ar
axis of said screw.
ranged substantially at right angles to the ?rst
10. In combination, a screw and a cooperating
helical wall and is located between the other pair nut, each provided with V-shaped threads, the 60
60 of opposing faces of the threads on said screw and
walls of said threads being arranged substan
tially at right angles to each other, a plurality
nut.
of rolling bearing elements arranged between op
3. A screw comprising a spindle having a v
shaped thread formed thereon with the faces
thereof arranged substantially at 90 degrees to
posing faces of the threads on said nut and screw,
saidbearing elements comprising frusto-com'cal 65
65 each other, and a bearing race formed on one face
rollers having the apex of the generating cone
located substantially on the axis of the screw,
of said thread, said race being arranged so that
its lower edge is spaced from the root of said
thread.
.
and a retainer located between said screw and
L
4. A nut comprising a hollow member having
a V-shaped thread formed within the bore there
of, the faces of said thread being arranged sub
stantially at 90 degrees to each‘ other, and a
nut for maintaining said rollers in spaced rela
tion, each of said rollers being rotatably mounted 70
upon a bearing pin passing through the center
thereof and secured to said retainer.
:
J. BAKER.
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